The present invention relates to an optical ferrule adapted for use in optical fiber connectors, optical measuring instruments and the like.
Hitherto, such an optical ferrule as shown in FIG. 1 has been known. This optical ferrule is adapted for use in a SC type optical fiber connector and includes a stainless steel collar 2 having a large through bore of a large inner diameter for receiving one end portion of a nylon coated optical fiber 1. The optical ferrule includes a ceramic sleeve 4 press fitted into the large through bore of steel collar 2, sleeve 4 and having a small through bore for receiving an bare optical fiber 3 extending from the end of the nylon coated optical fiber. The nylon coated optical fiber 1 and the bare fiber 3 are fixed to the stainless steel collar 2 and the ceramic sleeve 4 by an adhesive 5, respectively.
An optical ferrule of another type as shown in FIG. 2 has been proposed. In this optical ferrule, a nylon coated optical fiber 1 and its bare fiber 3 are inserted into a ceramic sleeve 4 without use of a stainless collar and fixed to the sleeve 4 by an adhesive 5.
However, when the optical ferrule shown in FIG. 1 is utilized with an optical electromagnetic measuring instrument, measurements are adversely affected by the stainless steel collar thereby reducing accuracy. Furthermore, the stainless steel collar 2 may corrode over a period of time thereby decreasing durability and reliability. Furthermore, the sleeve and the nylon coated optical fiber which are forcedly inserted into the stainless steel collar, may come out of the collar when the collar is expanded at a high temperature.
The optical ferrule shown in FIG. 2 does not have no disadvantages mentioned above such as deterioration of measurement accuracy and lack of durability owing to corrosion, since a stainless steel collar is not provided. But, in the arrangement as shown in FIG. 2, if the nylon coated optical fiber 1 repeatedly expands and contracts from temperature variations, the bare fiber 3 is extended from and retracted into the sleeve 4 or is broken down and comes out of the sleeve 4, thus decreasing reliability.